In production of semiconductor devices, an electron beam exposure technique receives a great deal of attention as a promising candidate of lithography capable of micro-pattern exposure at a line width of 0.1 μm or less. There are several electron beam exposure methods. An example is a variable rectangular beam method of drawing a pattern with one stroke. This method suffers many problems as a mass-production exposure apparatus because of a low throughput. To attain a high throughput, there is proposed a pattern projection method of reducing and transferring a pattern formed on a stencil mask. This method is advantageous to a simple repetitive pattern but disadvantageous to a random pattern such as a logic interconnection pattern in terms of the throughput, and a low productivity disables practical application.
To the contrary, a multi-beam system for drawing a pattern simultaneously with a plurality of electron beams without using any mask has been proposed and is very advantageous for practical use because of the absence of physical mask formation and exchange. What is important in using multi-electron beams is the number of electron lenses formed in an array used in an electron optical system. The number of electron lenses determines the number of electron beams, and is a main factor which determines the throughput. Downsizing while improving the performance of the electron optical system array is one of the keys to improving the performance of the multi-beam exposure apparatus.
Electron lenses are classified into electromagnetic and electrostatic types. The electrostatic electron lens does not require any coil core or the like, is simpler in structure than the electromagnetic electron lens, and is more advantageous to downsizing. Principal prior arts concerning downsizing of the electrostatic electron lens (electrostatic lens) will be described.
U.S. Pat. No. 4,419,580 proposes an electron optical system array in which electron lenses are two-dimensionally arrayed on an Si substrate and electrodes are aligned by V-grooves and cylindrical spacers. K. Y. Lee et al. (J. Vac. Sci. Technol. B12(6), November/December 1994, pp. 3,425-3,430) disclose a multilayered structure of Si and Pyrex glass fabricated by using anodic bonding, and provides microcolumn electron lenses aligned at a high precision.
In the electron optical system array disclosed in U.S. Pat. No. 4,419,580, Si substrates that are processed thin must be stacked. The fabrication process becomes difficult at a small electrode interval, and the multilayered structure is low in strength.
The electron optical system array disclosed by K. Y. Lee et al. suffers various problems which should be solved, such that 1) glass may not be sandwiched at a small electrode interval, and 2) anodic bonding must be repeated many times and the process is complicated (bonding must be repeated 2(n−1) times).